1. Field of the Invention
The present invention is directed to an improvement in a vehicle brake mechanism and more specifically to a roller retainer for a cam actuated brake assembly.
The invention is particularly useful in a brake assembly of the type disclosed in U.S. Pat. No. 4,206,834. That brake assembly includes a pair of brake shoes having adjacent ends pivotally mounted to a support and a rotatable actuating cam disposed between the other ends of the brake shoes. A roller-type cam follower is provided between each of those other ends of the brake shoes and the actuating cam. The roller-type cam followers are seated in open-ended recesses provided to the brake shoes. Rotary movement of the actuating cam is applied to the roller-type cam followers which cause their respective brake shoes to pivot outwardly about their pivot or anchor pins to contact the inwardly facing friction surface of a brake drum.
The roller-type cam followers are comprised of a stepped cylindrical steel pin having a center portion which bears against the actuating cam and smaller diameter end portions which serve as tunnions seated in the open ended recess provided to the spaced webs of a dual web brake shoe. Under normal conditions, the roller-type cam follower is trapped between the open ended recesses provided to the dual web brake shoe and the bearing surface of the actuating cam and held in that arrangement by the brake return spring. However, the brake assembly is comprised of a number of different parts and it is also advantageous to maintain the cam followers in the recesses provided to the brake shoes during assembly and disassembly of the brake mechanism for repair purposes. This limits the number of parts the mechanic has to be concerned with at any given time and the attendant possibility of dropping and losing the relatively small cam-follower rollers.
It has also become known that means for retaining a roller between the actuating cam and the open recesses provided to the ends of the brake shoe is also beneficial under conditions where the brake assembly is not maintained in adjustment particularly during extremely cold weather. Under such conditions, rollers have become displaced from their position in the open-ended recesses of the brake shoe webs which of course adversely affects operation of the brake assembly.
It is also desirable for assembly and maintenance purposes if the roller retaining means allow the cam-follower rollers to be applied and removed without the use of any tools.
2. Description of the Prior Art
U.S. Pat. No. 3,114,437 discloses one method of retaining a roller-type cam follower in open-ended recesses provided to brake shoes. In that patent the mouth of the open-ended recesses is formed to retain the ends of the rollers and a tool such as a screw driver may be required to remove the rollers from the brake shoes.
A spring has also been employed to retain a roller in its brake during transfer and assembly. The prior art spring retained the roller satisfactorily but the roller could not be withdrawn from the brake assembly without risk of injury to the mechanic's hand. The distance required for the retainer spring to clear other components of the brake assembly is such that a screwdriver or other tool was often used as a pry bar to expand the return spring.